2009-04-17  Ed Schonberg  <schonberg@adacore.com>

	* einfo.ads, einfo.adb: New attribute Underlying_Record_View, to handle
	type extensions whose parent is a type with unknown discriminants.

	* exp_aggr.adb (Expand_Record_Aggregate): If the type of an extension
	aggregate has unknown discriminants, use the Underlying_Record_View to
	obtain the discriminants of the ancestor part.

	* exp_disp.adb (Build_Dispatch_Tables): Types that are
	Underlying_Record_Views share the dispatching information of the
	original record extension.

	* exp_ch3.adb (Expand_Record_Extension): If the type inherits unknown
	discriminants, propagate dispach table information to the
	Underlying_Record_View.

	* sem_ch3.adb (Build_Derived_Private_Type): If parent type has unknown
	discriminants and declaration is not a completion, generate
	Underlying_Record_View to provide proper discriminant information to
	the front-end and to gigi.

From-SVN: r146264